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Extreme Intermittent Fasting May Pose Heart Risks, New Study Warns

Individuals limiting their daily eating window to fewer than eight hours faced a 135% higher risk of cardiovascular mortality compared to counterparts who ate across a 12–14 hour span.

• By Newsdesk
• New Delhi
• Sep 01, 2025

News

A newly published study has raised serious questions about ultra-strict intermittent fasting (IF) regimens. Data from over 19,000 U.S. adults—collected via the National Health and Nutrition Examination Survey (NHANES) between 2003 and 2018 and tracked over a median of eight years—reveals a startling trend: individuals limiting their daily eating window to fewer than eight hours faced a 135% higher risk of cardiovascular mortality compared to counterparts who ate across a 12–14 hour span.

Key Findings & Context

• This increased risk remained consistent across various demographics, including age, sex, race, socioeconomic status, and lifestyle factors. It was notably more pronounced in smokers, individuals with diabetes, and those with pre-existing heart conditions.
• Importantly, the study found no significant correlation between extreme time-restricted eating and overall mortality or cancer-related deaths.
• Lead researcher Prof. Victor Wenze Zhong emphasized the contrast with short-term studies that often highlight cardiovascular benefits, calling instead for more personalized dietary guidance over a blanket approach.

Expert Perspectives and Limitations

While the findings are alarming, experts caution against drawing definitive conclusions. The study’s observational design precludes causation claims. Dr. Sudhir Kumar—a neurologist trained at CMC Vellore—pointed out that inaccuracies in self-reported diet patterns or unaccounted underlying illnesses could have skewed results; for instance, people already unwell may unintentionally restrict food intake, influencing outcomes.

Simultaneously, endocrinologist Dr. Anoop Misra acknowledged that intermittent fasting can offer benefits like weight loss, improved insulin sensitivity, lower blood pressure, and reduced inflammation—but warned that overly restricted eating may introduce risks like nutrient deficiencies, irritability, and challenges for older adults or those with chronic ailments.

What Does This Mean for Fasting Enthusiasts?

This new data doesn’t call for abandoning intermittent fasting entirely. Rather, it advocates for sensible moderation, such as maintaining a more balanced eating window—like 10 to 12 hours—that may retain benefits while reducing potential harm.